Fire resistant file cabinets and safes, and method of manufacture thereof

ABSTRACT

Fire-rated file cabinets and safes manufactured by positioning sections of rigid, fire-resistant board into a fire-resistant frame.

FIELD OF THE INVENTION

The invention is directed to fire resistant, or fire-rated, file cabinets and safes. In particular, the invention is directed to fire-rated file cabinets and safes manufactured by positioning sections of rigid, fire-resistant board into a fire-resistant frame.

BACKGROUND OF THE INVENTION

Typically, fire-rated file cabinets and safes are made by casting a material that hardens by drying and curing, such as gypsum or cementitious products, in a complete cabinet form. Then, the hardware required for drawers and doors is inserted into the interior of the form. The entire form then is surrounded by a shell, typically of sheet metal.

Typically, water, gypsum, and minor additives, for example, to control hydration or foaming, are mixed to form a slurry. The slurry then is pumped into molds in which cavities are formed for drawers, if desired. This casting becomes the interior of the cabinet, and is surrounded by the shell.

This method of construction is both costly and time-consuming. Large molds of various sizes and shapes are required to make fire resistant filing cabinets and safes of different sizes and shapes. Also, the large castings are slow to dry and cure, thus requiring a long drying period. Further, the density of such a large casting typically exceeds 70 lbs. per cubic foot of material. Thus, such products are heavy and difficult to transport.

Various construction techniques have been applied in an effort to simplify construction of fire resistant file cabinets and safes. For example, U.S. Pat. No. 5,152,231 discloses a fire resistant safe comprising resinous shells filled with insulation materials. Typically, when exposed to a fire, the resin melts or is burned away and destructive air drafts form. However, in accordance with this patent, the paths in which these destructive air currents form are made too narrow to promote formation of the destructive air currents.

U.S. Pat. No. 6,044,776 and related patents disclose a modular safe. The various parts of the shell of a safe are made by filling hollow plastic panels shaped to form various walls, doors, tops and other parts of the cabinet filled with high-density concrete and reinforcing mesh. After the panels dry, the panels are bolted together to form modular security safes. Thus, the methods disclosed in these patents requires drying and curing of large panels disclosed enclosed in resin or plastic.

Modular concrete vaults are disclosed in U.S. Pat. No. 3,732,831. The vaults comprise prefabricated, reinforced concrete panels forming a ceiling, floor, and side walls. The panels include features added to the edges so that the panels can be joined quickly and securely.

A fire-resistant gun cabinet is disclosed in U.S. Patent Application Publications Nos. 2003/1418794 and 2003/0094885. The cabinet comprises a steel shell. Panels of fire-resistant material, such as magnesium board, sheetrock, gypsum board, or drywall (wall board), are attached to the inner walls of the metal shell, and can be spaced from the steel wall by small blocks. Such assembly relies on the metal shell for structural strength.

Another modular approach to vault construction is disclosed in U.S. Pat. No. 5,813,174. The structure comprises a modular tubular structure adapted to receive interlocking modular metal wall segments. The interior of the structure can be lined by attaching gypsum board to the interior surfaces of the structure. The structure is intended to be fixed in place, for example, by being bolted to the floor on which the vault rests.

None of these disclosures relates to producing a fire-resistant cabinet or safe that is relatively light compared with cabinets or safes of approximately equal fire resistance produced by known methods. Thus, there exists a need for fire resistant file cabinets and safes that are easily, quickly, and economically manufactured to provide a light weight fire resistant fire cabinet or safe.

BRIEF SUMMARY OF THE INVENTION

The invention relates to fire resistant file cabinets and safes. In particular, the invention is directed to fire resistant file cabinets and safes that are easily and economically manufactured using a fire resistant framework and pre-formed, rigid, fire-resistant board. Whereas a four-drawer fire resistant file cabinet made by casting typically weighs about 600 lbs., a cabinet of the invention could be expected to weigh between about 450 to 500 lbs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a front frame for a four-drawer filing cabinet of the invention.

FIG. 2 illustrates an embodiment of a front sub-frame for a four-drawer filing cabinet of the invention.

FIG. 3 illustrates an embodiment of a back ladder for a four-drawer filing cabinet of the invention.

FIG. 4 illustrates an embodiment of a rear frame for a four-drawer filing cabinet of the invention.

FIG. 5A illustrates the fit of the top board of a filing cabinet of the invention.

FIG. 5B illustrates a cross-section of a partially assembled filing cabinet of the invention.

FIG. 6 illustrates tie members and boards in place for a partially-assembled four-drawer filing cabinet.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to fire resistant file cabinets and safes made from conveniently available materials without requiring the curing and drying of a large fire proof casting, such as a gypsum casting. Fire resistant file cabinets and safes of the invention thus are easily made, requiring only a fire resistant framework, a cabinet shell, and preformed rigid fire resistant boards. Thus there is no need to prepare a slurry and cast a large and complex form.

Typically, in accordance with the invention, the fire resistant framework is metal and the rigid, fire resistant board is gypsum. The term “rigid” means resistant to bending and not flexible, i.e., unable to accommodate sharp bends. Typically-available gypsum sheets, for example, are ‘rigid’ for the purposes of the invention.

Fire resistant file cabinets and safes of the invention are quickly made, as there is no need to wait for a large casting to cure. Fire resistant filing cabinets and safes of the invention are economical, as they are readily made from commonly-available commercial products, such as gypsum board and preformed metal shapes.

Fire resistant filing cabinets and safes of the invention comprise a metal frame structure and preformed fire-resistant boards that form an interior structure, all of which is enclosed within a shell. Thus, the interior structure is surrounded by an exterior shell of choice, typically metal. The metal frame structure provides support for the pre-formed boards and for the exterior. Preferably, the boards are received into openings in the frame. Fire resistant filing cabinets and safes of the invention have a closeable opening for accessing the interior of the structure.

Skilled practitioners recognize that a safe or filing cabinet product can be made to have many arrangements of interior dividers, drawers, and doors. Skilled practitioners also recognize that such products can be made in any size or shape. For example, filing cabinets typically have one to five drawers. The drawers often are, but need not be, the same size. The invention is described and illustrated herein as an embodiment that is a four-drawer filing cabinet having different-sized drawers. However, the invention is not limited to four-drawer filing cabinets having different sized drawers, but also relates to filing cabinets of any size having any number of drawers of same or different sizes and to safes. “Safes” includes fire-resistant enclosures for articles of any type, such as gun cases. Skilled practitioners will recognize how to make and use other embodiments of the invention with the guidance provided herein.

The metal frame structure serves to hold the preformed boards in place to form a top, a bottom, a back, and two side walls of the fire resistant filing cabinet or safe of the invention. The front of the frame not only supports preformed boards in place, but also supports at least one closure of at least one opening for accessing the interior of the fire resistant filing cabinet or safe. Also, the metal frame holds dividing boards in place between optional drawers or subsections of the fire resistant filing cabinet or safe.

The frame is made of metal sufficient to support the pre-formed fire resistant boards and metal exterior. All three sub-parts working together are selected to be sufficient to provide the desired level of fire resistance.

Skilled practitioners recognize that there exist various tests and standards for measuring and expressing the level of protection provided by a fire-resistant filing cabinet or safe. These tests require that the interior of the product being tested not exceed a pre-selected temperature after a pre-selected period in a furnace at a higher pre-selected temperature. Often, the period used in fire resistant testing is ½ hour or 1 hour.

Underwriters' Laboratory (“UL”) has established standards and guidelines for such testing. “Tests for Fire Resistance of Record Protection Equipment,” UL-72, is one such standard. These tests identify three classes of protection: for paper records (Class 350); for paper and non-paper records such as EDP media (magnetic tapes) and photographic records (Class 150); and Class 150 items and flexible computer disks (Class 125).

Tests with and without surface impact resistance are described. The fire-resistant object being tested is placed on surface in a furnace so that five sides of the container are exposed to elevated temperature. The temperature in the furnace is controlled to achieve a pre-selected temperature throughout a selected period. With the guidance provided herein, the skilled practitioner will be able to identify a test procedure by which to test a fire-resistant safe or filing cabinet.

Suitable metals for the frame of fire resistant filing cabinets and safes of the invention include, for example, steel, cast and wrought iron, aluminum, and alloys. For example, stainless steel can be utilized. The metal can be formed in any suitable manner for forming metal into a desired shape.

Skilled practitioners recognize that aluminum is not very dense and would therefore provide a light weight frame. However, skilled practitioners also recognize that the melting point of aluminum, typically between about 900-1100 degrees F. for typical alloys, is significantly lower than the melting point of steel (about 2600 degrees F.). Therefore, a frame made from aluminum will provide only limited resistance to fire and heat. Aluminum-containing alloys may be suitable, but typically would be very expensive relative to typical steels. Similarly, stainless steels typically are relatively expensive as compared with typical steels. Therefore, stainless steels typically are not used.

The frame is made from a metal that provides the desired combination of strength, weight, and cost. Therefore, the thickness of the metal is selected to provide the desired strength and temperature resistance. With the guidance provided herein, the skilled practitioners can select a suitable metal from which to form the frame.

Preferably, a metal frame is made from sheet steel of suitable weight formed in to the desired shapes. Steel provides a good balance of strength, weight, workability, and cost. The thickness of the steel is related to the strength required and to fire resistance the cabinet or safe must demonstrate. For example, preferred steel thicknesses are in a range of 20 to 24 gauge for a cabinet sufficient to provide one half hour of protection under UL-72 guidelines for non-impact fire resistance for class 350. More preferably, 22-gauge sheet steel is used for this level of protection. With the guidance provided herein, the skilled practitioner will be able to select frame thickness appropriate for other levels of fire and impact resistance. Preferably, the frame has openings that receive the boards to hold them in place.

The frame can be in any form that supports the pre-formed fire resistant boards to form, in conjunction with the shell, a fire resistant structure. Preferably, the frame has openings that receive the boards to hold them in place. Preferably, the metal frame is made from channel, i.e., a U-shaped form that holds the pre-formed board securely by receiving an edge of the board within the ‘U’. As described more fully below, 90 degree angles (L-shaped forms) also are useful in forming a frame for use in the invention, especially when used in combination with channels. When made of channel and 90 degree-angle material, as described more fully below, a cabinet or safe container having excellent fire resistance is made.

Preferably, the width of the channel is selected to equal the thickness of the board being supported. For example, if 1-inch thick board is to be used, the width of the channel preferably is about 1 inch. If the channel width equals the thicknesses of board, the board then is held snugly by the channel and is retained securely in place. Obviously, if the width of the channel is less than the thickness of the board, the board cannot be retained in full thickness in the channel. However, the board could be thinned to be received in the channel, if the proposed combination provides the desired fire resistance. If the channel is significantly wider than the thickness of the board, the board will not be retained securely within the channel. Failure to securely retain a board in a channel may leave gaps at the edges of the interior structure where fire resistant boards intersect or abut in the frame. Such gaps may reduce the fire resistance of the cabinet or safe thus made.

The front of the frame provides part of the support of the top, bottom, and both side boards. The front of the frame also provides part of the support for any internal dividers, such as dividers between drawers. If drawers are present, the front frame also provides part of the support for the drawer glide mechanisms. Drawer latches and locks also may be present on the front frame. The back frame also typically provides support for the boards and dividers and drawer glide mechanisms, if any are present. The skilled practitioner recognizes that other support systems for these features also may be used. For example, such a feature may be held in place by a support, as described herein, at one side and fire-resistant adhesive at the other side. These and other systems may be used in accordance with the invention.

The front sub-frame or the interior of the cabinet is fashioned to accommodate latches, locks, and other hardware required to provide closure for the opening. For example, the rigid board may be grooved to form a channel for a lock mechanism typically found on a file cabinet. Such grooves are of a depth and form that they do not compromise the fire resistance of the product. Also, the front sub-frame may accommodate latches, locks, and other hardware. With the guidance provided herein, skilled practitioners will be able to fit hardware into the interior of the cabinet.

A front frame for a 4-drawer fire resistant filing cabinet, viewed from the inside of the cabinet, is illustrated in FIG. 1. The front frame comprises vertical U-shaped channels 1 and 2 and horizontal U-shaped channels 3 and 4 oriented with the openings of the channels pointing away from the front, or toward the back, attached to a sub-frame 5. The front sub-frame accommodates the closure of the opening to the interior of the fire resistant filing cabinets. The precise design of the front sub frame is not critical to the claimed invention.

An embodiment of a sub-frame is illustrated in FIG. 2. For example, if, as illustrated in FIG. 2, the front sub-frame is designed to accommodate four drawers, the sub-frame will further comprise two generally parallel side members 11, 12 spaced apart by 2 generally parallel horizontal members defining an opening large enough to accommodate the drawers. The sub frame also typically would have an appropriate number of dividers channels, here three, identified as reference numerals 15 and 16, and 17 in FIG. 1, horizontally disposed between the vertical members. Each divider channel will have its opening facing away from the front, i.e., into the interior of the cabinet, to receive a divider board. The sub-frame also typically is designed to attach to the exterior shell as described below. Drawer glide mechanisms also may be attached at the front to the sub frame. Vertical channels 1 and 2 are generally as long as the fire resistant board that will form the side of the interior cabinet structure, and are vertically disposed at the sides of the frame. Thus, the distance between the channels defines the interior width of the interior cabinet structure.

Horizontal channels 3 and 4 are disposed at the top and bottom, respectively, of the vertical channels, as shown in FIG. 1. Thus, it can be seen in FIG. 5A that the length of channel 3 is approximately the interior width of the interior structure. As illustrated in FIG. 5A for the top and further described below, for this embodiment, the top fire resistant board is as wide as the interior width plus the thickness of each of the side boards.

The rear frame of the four-drawer file cabinet embodiment is illustrated in FIGS. 3 and 4. Because the back must accommodate both the back board and each side board, channels must be present to accommodate each of these boards.

FIG. 3 illustrates one embodiment of a back ladder of the invention. U-shaped channel members 21 and 22 are oriented with their openings pointing forward, so as to receive the side boards. Horizontal channels 23 and 24 are disposed generally horizontally between vertical members 21 and 22 at their tops and bottoms, respectively. The horizontal channels are as wide as the top and bottom, respectively. Thus, as can be seen, the corners of each of the vertical channels 21 and 22 and horizontal channels 23 and 24 must be formed in a manner that accepts at the width of the bottom and of the top. One suitable method would be to cut the bottom portion of the interior side of vertical channels 21 and 22 to accommodate the thickness of the bottom, and similarly at the top. Another suitable method would be to miter the corners of each member, i.e., cut each at a 45 degree angle. With the disclosure herein skilled practitioners will recognize a number of ways to accommodate the boards. The precise detail of this feature is not critical, so long as the integrity of the fire resistant chamber is not compromised.

An embodiment of a frame for receiving the backboard is illustrated in FIG. 4. As illustrated in FIG. 4, vertical U-shaped channel members 21 and 22 of the back ladder 51 are attached to the inside of a larger L-shaped members 41 and 42, respectively, so as to form two channels for receiving boards. U-shaped members 21 and 22 of the back ladder are attached to the interior of one leg of L shaped members 41 and 42, respectively, so that the distance between the back of the U-shaped channel and the other leg of the L-shaped member is able to accommodate thickness of the back panel. Alternatively, instead of one U-shaped channel and one L-shaped angle, two U-shaped channels could be oriented with the back of one channel attached to a side of the other channel. However, such an arrangement may be less fire-resistant than the structure previously described, as there exists the possibility of a gap between the back and side boards unless the joint between the U-shaped channels is completely sealed. Horizontal L-shaped members 43 and 44 are connected to the tops and buttoms, respectively, or vertical L-shaped members 41 and 42. Horizontal member 43 is shown in FIG. 5A, a top view of the illustrated cabinet.

Vertical channels 21 and 22 are slightly shorter than vertical L-shaped members 41 and 42 solely for manufacturing convenience. Generally, vertical channels 21 and 22 and vertical L-shaped members 41 and 42 are as long as the back fire resistant board, which extends from the top of the top board to the bottom of the bottom board in this embodiment. Thus, vertical channels 21 and 22 are longer than the side fire resistant boards. Horizontal channels 23 and 24 are oriented with respect to horizontal L-shaped members 43 and 44 just as vertical channels 21 and 22 are oriented with respect to vertical L-shaped members 41 and 42.

The back ladder also has channels that securely support any dividers. Channels to support any dividers are placed within the back ladder, typically between vertical channels 21, 22, so that the rear of the divider channel is flush with the rear of the vertical channel. These channels also can be used to secure the rear of any drawer glide mechanisms. Divider channels are illustrated on FIGS. 3 and 4 as reference numerals 24, 25, and 26.

The front frame and the rear frame are separate assemblies. The various channels and members of the front frame and the rear frame may be attached to each other in any manner that does not interfere with the assembly of the fire resistant file cabinets or safes of the invention, keeping in mind that the fire resistant boards are held within the channels.

The individual members of the front frame and of the rear frame may be welded, spot welded, riveted, adhered to, or attached to each other in any way that will allow for assembly, as described herein, and provide the requisite fire resistant structure. However, the method of attachment and assembly cannot preclude the insertion of a board into channels or into the area for the board to be received. Alternatively, if the channel is blocked by a fastener device such as a screw, for example, it would be necessary to notch the fire resistant board to go around the screw. Such notching or other board thickness reductions are acceptable only so long as they do not reduce fire resistance to an unacceptably low level. Alternatively, the screw or other attacher could be driven through a board already in place.

The front and rear frames are connected to each other in any suitable way to form, together with the fire resistant boards and exterior cabinet, the fire resistant filing cabinets and safes of the invention. The tie members hold the channels containing the board components together securely without the use of screws and other attachments that would otherwise need to be inserted into the edges and ends of the boards. In a preferred embodiment, the front frame and the rear frame are connected by tie members 7, 8 and 17, 18, as illustrated in FIG. 6. In accordance with this embodiment, the tie members also provide additional support for the side boards.

In a preferred embodiment, the tie members are of such a length and arrangement that various fire resistant boards are held securely in place between the frames, with the boards used to provide structural rigidity to the fire resistant filing cabinets or safes of the invention. In accordance with this embodiment, fire resistant boards are held under compression by the tie members and channels.

The precise manner by which the front and rear frames are attached is not critical to the invention. Tie members, braces, channels, and other manners of connecting the front and rear frames are acceptable. These members contribute to the structural rigidity of the fire resistant filing cabinet or safe of the invention. Any manner of attachment is acceptable, so long as the fire resistance of the product is maintained as they hold the component together. The tie members thus improve the structural integrity of the fire resistant safe or cabinet of the invention.

The relative sizes of the boards and the distance between the structures receiving the boards preferably are selected so that each board extends into the holder at least about one half of the thickness of the board, preferably at least about three-fourths of the thickness, and more preferably at least about seven eighths of the thickness. Therefore, with a 1″ thick board, at least about 0.5 in. of board is retained within the receiving structure. More preferably, at least about 0.75 inch of a 1″ board is retained, and most preferably at least about 0.875 in. of the board is retained. Most preferably, the retention depth is as great as possible to insure the integrity of the fire resistant container.

The invention has been described herein as comprising a front frame, a rear frame, and connections there between, together with fire resistant boards and an exterior cabinet. This manner of description is especially convenient, as the front frame provides support for the door, drawers, or other closures, and for dividers, as described herein. This method is particularly useful for a file cabinet with drawers. However, as skilled practitioners recognize, fire resistant filing cabinets and safes of the invention can be made by having frames at the sides of the container, with related edges of each side frame adapted to form a front of the container and to support a closure. Such side frames, which can be connected by tie members, also can provide support for drawer glide mechanisms and the dividers. With the guidance provided herein, a skilled practitioner can easily manufacture a fire resistant filing cabinet or safe of the invention having such side frames.

Fire resistant boards used in the invention are made of any fire resistant material and at any thickness that provides the desired degree of fire resistance. Suitable fire resistant boards typically are rigid. Preferably, the fire resistant board is gypsum. Gypsum board often is made with facing material. Facing materials typically include paper and woven and unwoven fabrics of natural and synthetic compositions, such as wood, plastics, and glass fibers. Such board is suitably used in the practice of the invention.

Plural layers of fire resistant board also can suitably be used to manufacture fire resistant file cabinets and safes of the invention. For example, to achieve a board thickness of 1 in., two ½ inch thick fire resistant boards can be used. Also, skilled practitioners recognize that the fire resistant boards need not all have the same thickness. For example, fire resistant dividers might be thinner than the fire resistant boards that make up the sides. Similarly, the top or the bottom fire resistant boards of a fire resistant filing cabinet or safe of the invention might be thinner or thicker than the other boards. As described herein, the thickness of the boards is established to provide a predetermined level of fire resistance.

Any suitable fire-resistant board can be used. Preferably, board with non-paper faces is utilized. One such board preferred in the practice of the invention is gypsum board having non-woven glass faces. Such board is available from Georgia-Pacific, Inc. Other fire-resistant board products also are suitable and can be identified by the skilled practitioner with the guidance provided herein.

Although the inventor does not wish to be bound by theory, it is believed that the preferred board is especially suitable for use in the invention because it has a high combined water content. The combined water content of the preferred board typically is between about 15 and 20%. Gypsum releases water when heated. This released water tends to cool the interior of a volume enclosed by a gypsum cabinet or safe. Thus, gypsum not only insulates against the heat and does not burn, but also it cools the interior of the safe or fire-resistant cabinet of the invention by releasing water vapor. Thus, a higher combined water concentration in the fire resistant components yields a greater cooling effect.

Skilled practitioners recognize, therefore, that a relatively high combined water content in gypsum products used to enclose and insulate a volume will provide greater protection against heat damage caused by a temperature increase in the enclosed volume. Thus, it is advantageous to use gypsum board products, inasmuch as the combined water concentration tends to be relatively high.

The fire resistant file cabinet or safe of the invention can be assembled in any convenient manner. In a preferred manner, fire resistant boards are put in place to form the top, sides, and bottom, together with any dividers, are put in place in the front frame. Then, the rear frame is put into place by sliding the frame over the boards already in place, guiding the boards into the channels of the frame. Then, the fire resistant board that forms the back of the container can be slid into the rear frame, with the top L-shaped member put in place thereafter. The side tie members are put into place after the rear frame is put in place, either before or after the back board is in place. The tie members are attached to both front and rear frames, thus securing the frames and boards and forming the interior structure.

As described above, plural layers of boards can be used to form the fire resistant walls of the container. In accordance with the invention, fire resistant boards also can be attached to the outside of the frame to provide another layer of fire resistance. Such additional boards can be used on some or all of the surfaces to provide additional fire resistance.

The precise manner by which such additional layers of fire resistant boards are attached to the frame is not critical to the invention. Inasmuch as this additional layer is attached to the frame after the frame is formed with the boards in place, it is possible to attach the additional layer to the skeleton by, for example, screwing the additional layer to the skeleton, such as to the channels, and to the L-shaped members in the rear frame. Any penetration of the boards held in place is not significant, so long as fire resistance is not compromised. Indeed, such additional attachments may lend additional rigidity and security to the structure, and may help anchor the boards in place. With the guidance provided herein, skilled practitioners will recognize the other ways of forming and assembling fire resistant file cabinets and safes of the invention are available.

The boards of plural layers need not be the same. Thus, different types and thickness of boards can be used within this scope of the invention. A preferred board for attachment to the frame as a second layer is a gypsum board product having a non-woven glass layer on both faces. Such a preferred product is available from Georgia-Pacific. With the guidance provided herein, skilled practitioners will be able to identify other suitable board products.

Various manners of attaching the various frame parts to a skeleton, and of assembling frames and fire resistant boards to form fire resistant file cabinets and safes of the invention in a suitable manner of forming a frame assembling them can be used to form fire resistant file cabinets and safes of the invention.

The interior structure is surrounded by a cabinet, typically a sheet metal cabinet. The precise design, structure, and composition of material of such a cabinet are not critical to the invention. Any suitable cabinet, shaped and formed to enclose and to be attached to the interior structure, is suitable.

Skilled practitioners recognize that the exterior cabinet forms an integral part of the fire resistant file cabinet or safe of the invention. The exterior cabinet provides a layer of fire resistance. Thus, typically a fire-resistant material is used to form the cabinet. Sheet metal is suitable. Typically, such metal will have a gauge of between about 20 and about 24. The inventors have found that 22-gauge sheet metal provides a suitable level of fire resistance without addition unnecessary weight to the fire resistant filing cabinet or safe of the invention.

EXAMPLE 1

A four-drawer filing cabinet was made in accordance with the invention and tested for fire resistance.

A front sub-frame was fabricated from sheet steel to accommodate four drawers. The sub-frame contained four drawer openings and three 1″×1″ U-shaped channels of 22-gauge sheet metal for receiving dividers between the drawers. The sub-frame also included locations at which to attach the cabinet exterior.

Four channels were added to the sub-frame to form the front-frame. Two vertical U-shaped channels 1″×1″×48¾″ were spot-welded to the sub-frame with the channel opening directed toward the rear of the cabinet, i.e., away from the front. Two horizontal U-shaped channels 1″×1″×16¾″ were centered between the vertical channels and the tops and bottoms thereof, so that the top and bottom fire-resistant boards were able to extend across the width of the interior structure, from the outside of one side fire-resistant board to the outside of the other side fire-resistant board.

The rear frame was made of 1″×1″ 22-gauge U-shaped channel and 22-gauge, 2″×2″ 90-degree angle, L-shaped, steel. Two pieces of angle steel 51″ long formed the vertical frame members. The vertical frame members were separated by 19″-long horizontal members. The members were mitred at 45 degree angles to fit together at the covers and were attached at the corners by spot-welding. The top member was attached after the back board was slid into place, as described below.

A rear ladder was formed from 1″×1″ U-shaped channels. Two vertical U-shaped channels 50⅞″ long were attached to the two 16⅞″ long horizontal U-shaped channels by spot-welding. The ends of these channels were mitred at 45 degrees, similar to the angle steel, to enable placement of the full-width top and bottom boards. Three 1″×1″ U-shaped channels for receiving the drawer dividers and drawer glide mechanisms, each 16⅞″ long, were attached by spot-welding to the vertical channels so that they spanned the distance between these channels.

The two vertical U-shaped channels were attached by spot-welding to the inside of the vertical frame members, one on each side, so that the front of the U-shape and the edge of the 2″×2″ angle steel were essentially aligned. Similarly, top and bottom U-shaped channels were attached in the same way. In this way, there remained a 1″ gap between the back of the U-channel and the inside of the other leg of the L-shaped member to accommodate a 1″ thick back board.

The following pieces of a 1″ thick gypsum board available from Georgia-Pacific having non-woven glass faces and a density of about 40 lbs. per square foot, were placed in the front frame:

2 Sides, each 1″×21⅝″×48⅞″

1 Top and 1 Bottom, each 1″×21⅝″×19″

3 Dividers 1″×21⅝″×16⅞″

After each of these boards was placed in the front frame, the various channels of the back frame were aligned with and carefully slid over the exposed edges of the various boards. The front frame and rear frame then were tied together with steel straps riveted to the front and rear frames. Then, the back board, measuring 1″×19″×51″, was slid into place, and the top angle piece was secured.

Then, the following additional gypsum-based boards with non-woven glass-fiber faces sold by Georgia-Pacific, and having a density of about 32 lbs. per square foot at the ½″ thickness used, were attached to the outside of the frames:

1 Top and 1 Bottom, each ⅝″×19″×24″

2 Sides, each ½″×24″×52¼″

Back ½″×20¼″×52¼″

The boards were attached by fire resistant adhesive.

While the invention has been described with respect to specific examples including preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims. One such change is described in the specification—use of side frames rather than front and rear frames. Other ways of assembling the frames, or of connecting such frames to form the required structure, also are known to skilled practitioners who, with the guidance provided herein, will be able to carry out the invention in numerous ways. 

1. A fire-resistant filing cabinet or safe comprising rigid pre-formed fire-resistant boards retained by a fire-resistant framework to form an enclosed fire resistant volume within an exterior shell, wherein, the boards comprise fire-resistant material of thickness and composition sufficient to provide a desired degree of fire resistance in combination with the framework and the shell, the framework comprises fire-resistant material of thickness and composition sufficient to provide a desired degree of fire resistance in combination with the fire resistant boards and the shell, said framework providing structural strength sufficient to retain the boards in place and maintain the shape of the filing cabinet or safe sufficient to obtain the desired fire resistance, and the shell covering the exterior of the filing cabinet.
 2. The cabinet or safe of claim 1, further comprising a divider forming an enclosed volume within the cabinet or safe.
 3. The cabinet or safe of claim 2, wherein the framework further comprises members to retain the divider.
 4. The cabinet or safe of claim 2, wherein the divider is held in place by fire-resistant adhesive.
 5. The cabinet or safe of claim 1, wherein the boards are received into openings in the framework.
 6. The cabinet or safe of claim 5, wherein the openings are slots formed by U-shaped channels or frame parts positioned so as to form a slot for receiving a board.
 7. The cabinet or safe of claim 1 wherein the boards comprise gypsum.
 8. The cabinet or safe of claim 1 wherein more than one layer of board is used.
 9. The cabinet or safe of claim 8 wherein at least one layer of board is attached to the outside of the framework and at least one layer of board is received in openings in the framework. 